The Rovers went up 1-0 in the sixth minute when striker Angus Kilkolly volleyed a goal past Peta from the top of the 18m box.
The ball had ballooned off a defender's leg to sit up for Kilkolly, who had tried to push a pass unsuccessfully to Canadian import Paulin Jean-Michel in a scissors move.
Three minutes before halftime, youngster James Barclay gave away an unnecessary penalty when he clipped Jean-Michel from behind considering the ball was rolling out of harm's way from the goal mouth.
Kilkolly stepped up to have Peta diving the wrong way for a 2-0 lead.
The Rovers went up 3-0 in the 54th minute from vice-captain Joshua Stevenson after a deft cross from his skipper, Fergus Neil.
The Wanderers, making Blues goalkeeper work a little after Greatholder's injection, eventually pulled one back one minute into referee Gareth Sheehan's time with a goal to Harrison Gregory.
Yesterday, Alexander Electrical Napier Marist Premiers came from 3-2 behind to beat Breakers Red Sox Manawatu 4-3 in Palmerston North.
It was drama in the 31st minute when Red Sox goal keeper Scott Outtrim was sent off in the 31st minute for running out to tackle a forager but, on coming up short, took him out to receive a straight red card.
Marist centreback Jonty Underwood also was sent off with three minutes to go with a sprigs-up tackle that Red Sox coach Neil Perry felt was born out of frustration.
The Jamie Dunning-coached Marist scored 1-0 in just 15 seconds after striker Thomas Tidy latched on to Sox centreback Paul Dalzell's clearance kick to set the match alight at Memorial Park.
Dunning said a bad patch followed, after the hosts conceded an own goal to trail 2-0, opening the way for Manawatu to claw their way back into the game.
Liam Patterson (20th), Ryan Noble (35th) and Brandon Jackson (43rd) pumped in goals for Red Sox to go into halftime 3-2 up.
"I told the boys you score early and you'll win the game," said Dunning as attacking midfielder Josh Murphy obliged in the 49th minute before leftwing back Dylan DuRoss sealed victory in the 67th.
Manawatu threw the kitchen at them but he felt they hadn't threatened Marist much.
"We just took in a nothing-to-lose attitude, actually," Dunning said when asked if the giant-killing tag was sitting well with the third-tier Computer Care HB Premiership team.
After upsetting Gisborne Thistle in the preliminaries, Marist will enter the second round. They ran on yesterday with the aim of having fun but Dunning was confident of a win against the second-tier Lotto Federation League side.
"We've beaten two teams in leagues above us to show what we can achieve depending on how far these boys can go in their careers," he said today.
A chuckling Dunning said his mainly youthful players would be crowing for a Rovers derby in round two but who knows what the hat will offer tomorrow.
Most of the Marist players often watched the Rovers play but some would have been spending time on Mother's Day today.
Perry felt the game could have gone either way but his troops, who lost three players to injuries during the game, started poorly.
"We scored three goals but we have to stop conceding goals," he said, putting it down to their worst performance this season even though they missed four one-on-one chances.
Conversely, Perry gave credit to Marist for putting Manawatu under pressure with their pace.
"They played well and thoroughly deserved their win," he said.
